A Hybrid Current- and Voltage-Source Driver for Active Driving of Series-Connected SiC MOSFETs

Abstract

The series-connection of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors ( mosfet s) is an attractive way of increasing the blocking voltage capability of a switch. However, due to inherent transient and steady-state voltage imbalance issues, such a design imposes challenges, especially at elevated switching frequencies, where increased dv/dt is required. This article proposes a hybrid gate driver for series-connected Silicon Carbide (SiC) mosfet s, which consists of a turn- on stage with a traditional voltage source gate driver (VSGD), and a turn- off sequence combining a Current Source Gate Driv er (CSGD) and a Voltage Source Gate Driver (VSGD). The proposed hybrid gate driver can actively control the turn- off dv/dt and di/dt of the switch by adjusting the amplitude of the gate current in the Current Source Gate Driver (CSGD) stage, as well as balance the voltages of the serialized switches by adjusting the timing delays in the driver. This adaptability enables switching loss control of the devices. The proposed driver has been experimentally validated for two series-connected SiC mosfet s. From experiments, it is shown that a voltage imbalance below 2% can be achieved at direct current (DC)-voltage of 1.5kV and that switching speeds can be adjusted between 20 and 70kV /µs, while the turn- off switching energy can be reduced by up to 41%.